This work received the financial support of Georgia Commodity Commission for Vegetables project ID# FP00016659. The authors thank Dr. Pingsheng Ji, University of Georgia and Dr. Anne Dorrance, Ohio State University for providing pure cultures of Phytophthora spp. We also thank Li Wang and Deloris Veney for their technical assistance throughout the study.

1. On-site detection of Phytophthora capsici from irrigation water using portable loop-mediated isothermal amplification
<ol>
	<li>Setting up the pump and filter
	<ol>
		<li>Attach a filtering flask to a tube that is connected to a hand pump so that when the pump is activated, air will be pulled in through the mouth of the filtering flask.</li>
		<li>Fit the Buchner funnel into the rubber stopper to the mouth of the filtering flask and fit the appropriately sized piece of filter paper into the Buchner funnel s...

<ol>
	<li>Hong, C., Moorman, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plant+pathogens+in+irrigation+water:+challenges+and+opportunities.">Plant pathogens in irrigation water: challenges and opportunities.</a> Critical Reviews in Plant Sciences. 24 (3), 189-208 (2005).</li><li>Malkawi, H. I., Mohammad, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physiology,+Genetics,+Morphology,+&amp;+Microorganisms,+E.+o.+Survival+and+accumulation+of+microorganisms+in+soils+irrigated+with+secondary+treated+wastewater.">Physiology, Genetics, Morphology, &amp; Microorganisms, E. o. Survival and accumulation of microorganisms in soils irrigated with secondary treated wastewater.</a> Journal of Basic Microbiology. 43 (1), 47-55 (2003).</li><li>Bush, E. A., Hong, C., Stromberg, E. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluctuations+of+Phytophthora+and+Pythium+spp.+in+components+of+a+recycling+irrigation+system.">Fluctuations of Phytophthora and Pythium spp. in components of a recycling irrigation system.</a> Plant Disease. 87 (12), 1500-1506 (2003).</li><li>Ghimire, S. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Distribution+and+diversity+of+Phytophthora+species+in+nursery+irrigation+reservoir+adopting+water+recycling+system+during+winter+months.">Distribution and diversity of Phytophthora species in nursery irrigation reservoir adopting water recycling system during winter months.</a> Journal of Phytopathology. 159 (11-12), 713-719 (2011).</li><li>Hausbeck, M. K., Lamour, K. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phytophthora+capsici+on+vegetable+crops:+research+progress+and+management+challenges.">Phytophthora capsici on vegetable crops: research progress and management challenges.</a> Plant Disease. 88 (12), 1292-1303 (2004).</li><li>Gevens, A., Donahoo, R., Lamour, K., Hausbeck, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+Phytophthora+capsici+from+Michigan+surface+irrigation+water.">Characterization of Phytophthora capsici from Michigan surface irrigation water.</a> Phytopathology. 97 (4), 421-428 (2007).</li><li>Thomson, S., Allen, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Occurrence+of+Phytophthora+species+and+other+potential+plant+pathogens+in+recycled+irrigation+water.">Occurrence of Phytophthora species and other potential plant pathogens in recycled irrigation water.</a> Plant Disease Reporter. 58 (10), 945-949 (1974).</li><li>Lamour, K. H., Stam, R., Jupe, J., Huitema, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+oomycete+broad-host-range+pathogen+Phytophthora+capsici.">The oomycete broad-host-range pathogen Phytophthora capsici.</a> Journal of Molecular Plant Pathology. 13 (4), 329-337 (2012).</li><li>Sanogo, S., Ji, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Water+management+in+relation+to+control+of+Phytophthora+capsici+in+vegetable+crops.">Water management in relation to control of Phytophthora capsici in vegetable crops.</a> Agricultural Water Management. 129, 113-119 (2013).</li><li>Zhang, Z., Li, Y., Fan, H., Wang, Y., Zheng, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+detection+of+Phytophthora+capsici+in+infected+plant+tissues,+soil+and+water.">Molecular detection of Phytophthora capsici in infected plant tissues, soil and water.</a> Plant Pathology. 55 (6), 770-775 (2006).</li><li>Trout, C., Ristaino, J., Madritch, M., Wangsomboondee, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+detection+of+Phytophthora+infestans+in+late+blight-infected+potato+and+tomato+using+PCR.">Rapid detection of Phytophthora infestans in late blight-infected potato and tomato using PCR.</a> Plant Disease. 81 (9), 1042-1048 (1997).</li><li>Sankaran, S., Mishra, A., Ehsani, R., Davis, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+review+of+advanced+techniques+for+detecting+plant+diseases.">A review of advanced techniques for detecting plant diseases.</a> Commputers and Electronics in Agriculture. 72 (1), 1-13 (2010).</li><li>Wang, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+an+improved+isolation+approach+and+simple+sequence+repeat+markers+to+characterize+Phytophthora+capsici+populations+in+irrigation+ponds+in+southern+Georgia.">Development of an improved isolation approach and simple sequence repeat markers to characterize Phytophthora capsici populations in irrigation ponds in southern Georgia.</a> Applied and Environmental Microbiology. 75 (17), 5467-5473 (2009).</li><li>Ali-Shtayeh, M., MacDonald, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Occurrence+of+Phytophthora+species+in+irrigation+water+in+the+Nablus+area+(West+Bank+of+Jordan).">Occurrence of Phytophthora species in irrigation water in the Nablus area (West Bank of Jordan).</a> Phytopathologia Mediterranea. , 143-150 (1991).</li><li>Pringsh, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+serological+and+culture+plate+methods+for+detecting+species+of+Phytophthora,+Pythium,+and+Rhizoctonia+in+ornamental+plants.">Comparison of serological and culture plate methods for detecting species of Phytophthora, Pythium, and Rhizoctonia in ornamental plants.</a> Plant Disease. 74 (9), 655 (1990).</li><li>Stewart-Wade, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plant+pathogens+in+recycled+irrigation+water+in+commercial+plant+nurseries+and+greenhouses:+their+detection+and+management.">Plant pathogens in recycled irrigation water in commercial plant nurseries and greenhouses: their detection and management.</a> Irrigation Science. 29 (4), 267-297 (2011).</li><li>Aragaki, M., Uchida, J. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Morphological+distinctions+between+Phytophthora+capsici+and+P.+tropicalis+sp.+nov.">Morphological distinctions between Phytophthora capsici and P. tropicalis sp. nov.</a> Mycologia. 93 (1), 137-145 (2001).</li><li>Tomlinson, J., Boonham, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Potential+of+LAMP+for+detection+of+plant+pathogens.">Potential of LAMP for detection of plant pathogens.</a> CAB Reviews Perspectives in Agriculture Veterinary Science Nutrition and Natural Resources. 3 (066), 1-7 (2008).</li><li>Li, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+PCR-based+assay+for+distinguishing+between+A1+and+A2+mating+types+of+Phytophthora+capsici.">A PCR-based assay for distinguishing between A1 and A2 mating types of Phytophthora capsici.</a> Journal of the American Society for Horticultural Science. 142 (4), 260-264 (2017).</li><li>Dong, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Loop-mediated+isothermal+amplification+assay+for+sensitive+and+rapid+detection+of+Phytophthora+capsici.">Loop-mediated isothermal amplification assay for sensitive and rapid detection of Phytophthora capsici.</a> Canadian Journal of Plant Pathology. 37 (4), 485-494 (2015).</li><li>Khan, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+evaluation+of+the+LAMP+assay+and+PCR-based+assays+for+the+rapid+detection+of+Alternaria+solani.">Comparative evaluation of the LAMP assay and PCR-based assays for the rapid detection of Alternaria solani.</a> Frontiers in Microbiology. 9, 2089 (2018).</li><li>Sowmya, N., Thakur, M., Manonmani, H. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+and+simple+DNA+extraction+method+for+the+detection+of+enterotoxigenic+Staphylococcus+aureus+directly+from+food+samples:+comparison+of+PCR+and+LAMP+methods.">Rapid and simple DNA extraction method for the detection of enterotoxigenic Staphylococcus aureus directly from food samples: comparison of PCR and LAMP methods.</a> Journal of Applied Microbiology. 113 (1), 106-113 (2012).</li><li>Waliullah, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+analysis+of+different+molecular+and+serological+methods+for+detection+of+Xylella+fastidiosa+in+blueberry.">Comparative analysis of different molecular and serological methods for detection of Xylella fastidiosa in blueberry.</a> PLOS ONE. 14 (9), 0221903 (2019).</li><li>B&#246;hm, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Real-time+quantitative+PCR:+DNA+determination+in+isolated+spores+of+the+mycorrhizal+fungus+Glomus+mosseae+and+monitoring+of+Phytophthora+infestans+and+Phytophthora+citricola+in+their+respective+host+plants.">Real-time quantitative PCR: DNA determination in isolated spores of the mycorrhizal fungus Glomus mosseae and monitoring of Phytophthora infestans and Phytophthora citricola in their respective host plants.</a> Journal of Phytopathology. 147, 409-416 (1999).</li><li>Klimczak, L., Prell, H. J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+characterization+of+mitochondrial+DNA+of+the+oomycetous+fungus+Phytophthora+infestans.">Isolation and characterization of mitochondrial DNA of the oomycetous fungus Phytophthora infestans.</a> Current Genetics. 8 (4), 323-326 (1984).</li><li>Ghimire, S. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detection+of+Phytophthora+species+in+a+run-off+water+retention+basin+at+a+commercial+nursery+in+plant+hardiness+zones+7+b+of+Virginia+in+winter.">Detection of Phytophthora species in a run-off water retention basin at a commercial nursery in plant hardiness zones 7 b of Virginia in winter.</a> Phytopathology. 96 (6), (2006).</li><li>Feng, W., Hieno, A., Kusunoki, M., Suga, H., Kageyama, K. J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=LAMP+detection+of+four+plant-pathogenic+oomycetes+and+its+application+in+lettuce+fields.">LAMP detection of four plant-pathogenic oomycetes and its application in lettuce fields.</a> Plant Disease. 103 (2), 298-307 (2019).</li><li>Aglietti, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Real-time+loop-mediated+isothermal+amplification:+an+early-warning+tool+for+quarantine+plant+pathogen+detection.">Real-time loop-mediated isothermal amplification: an early-warning tool for quarantine plant pathogen detection.</a> AMB Express. 9 (1), 50 (2019).</li><li>Almasi, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+colorimetric+loop-mediated+isothermal+amplification+assay+for+the+visual+detection+of+Fusarium+oxysporum+f.+sp.+melonis.">Development of a colorimetric loop-mediated isothermal amplification assay for the visual detection of Fusarium oxysporum f. sp. melonis.</a> Horticultural Plant Journal. 5 (3), 129-136 (2019).</li><li>Gill, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pathogenic+Pythium+from+irrigation+ponds.">Pathogenic Pythium from irrigation ponds.</a> Plant Disease Reporter. 54 (12), 1077-1079 (1970).</li></ol>

The authors have nothing to disclose or any conflicts of interest.

The testing of irrigation water for phytopathogens is a crucial step for growers using irrigation ponds and recycled water27. Irrigation ponds provide a reservoir and breeding ground for a number of phytopathogens as excess irrigation water is directed from the field to the pond carrying with it any pathogens that may have been present16,27. The traditional method for detection of a plant pathogens in a large water source is to set a bait ...

Recycling water in farms and nurseries is becoming increasingly popular due to the increase in water costs and environmental concerns behind water usage. Many irrigation methods have been developed for growers to reduce the spread and occurrence of plant disease. Regardless of the source of the water (irrigation or precipitation), runoff is generated, and many vegetable and nursery growers have a pond to collect and recycle runoff1. This creates a reservoir for possible pathogen accumulation favoring the spread of pathogens when the recycled water is used to irrigate crops2,3,4. Oomycete plant pathogens particularly benefit from this practice as zoospores will accumulate in water and the primary dispersive spore is self-motile but requires surface water5,6,7. Phytophthora capsici is an oomycete pathogen that affects a significant number of solanaceous and cucurbit crops in different ways8. Often, the symptoms are damping-off of seedlings, root and crown rot; however, in crops such as cucumber, squash, melon, pumpkin, watermelon, eggplant and pepper, entire harvests may be lost due to fruit rot9. Although there are known methods of detecting this plant pathogen, most require an infection to have already taken place which is too late for any preventative fungicides to have a significant effect10.
The traditional method to test irrigation water for the detection and diagnosis of targeted microorganisms is an antiquated approach when speed and sensitivity are crucial to success and profitable crop production11,12. Plant tissue susceptible to the targeted pathogen (e.g., eggplant for P. capsici) is attached to a modified trap that is suspended in an irrigation pond for extended period before being removed and inspected for infection. Samples from the plant tissue are then plated on semi-selective media (PARPH) and incubated for culture growth, then morphological identification is performed using a compound microscope13. There are other similar detection methods for other plant pathogens using selective media and plating small amounts of contaminated water before sub-culturing14,15. These methods require anywhere from 2 to 6 weeks, several rounds of sub-culturing to isolate the organism, and experience on Phytophthora diagnostics to be able to recognize the key morphological characters of each species. These traditional methods do not work well for detection of irrigation water contaminated by P. capsici due to factors such as interference by other microorganisms that are also present in the water sources. Some fast-growing microorganisms like Pythium spp. and water-borne bacteria can overgrow on the plate making P. capsici undetectable16,17.
The purpose of this study was to develop a sensitive and specific molecular method that can be used in both field and laboratory settings to detect P. capsici zoospores in irrigation water. The protocol includes the development of a novel loop-mediated isothermal amplification (LAMP) primer set able to specifically amplify P. capsici, based on a 1121-base pair (bp) fragment of P. capsici18,19. A previously developed LAMP primer from Dong et al. (2015) was used in comparison to the assay that was developed for this study20.
The LAMP assay is a relatively new form of molecular detection that has been demonstrated to be more rapid, sensitive, and specific than conventional polymerase chain reaction (PCR)21. In general, conventional PCR assays cannot detect under 500 copies (1.25 pg/&#181;L); in contrast, previous studies have shown that the sensitivity of LAMP can be 10 to 1,000 times higher than conventional PCR and can easily detect even 1 fg/&#181;L of genomic DNA22,23. Additionally, the assay can be carried out rapidly (often in 30 min) and on-site (in the field) by using a portable heating block for amplification and a colorimetric dye that changes color for a positive sample (removing the need for electrophoresis). In this study, we compared the sensitivity of PCR and LAMP assays using a filter extraction method. The proposed detection method allows researchers and extension agents to easily detect the presence of P. capsici spores from different water sources in less than two hours. The assay is proven to be more sensitive than conventional PCR and was validated in situ by detecting the presence of the pathogen in the irrigation water used by a grower. This detection method will allow growers to estimate the presence and population density of the pathogen in various water sources that are being used for irrigation, preventing devastating outbreaks and economic losses.

<table>
	<tbody>
		<tr>
			<td>Agarose gel powder</td>
			<td>Thomas Scientific</td>
			<td>C997J85</td>
			<td></td>
		</tr>
		<tr>
			<td>Buchner funnel</td>
			<td>Southern Labware</td>
			<td>JBF003</td>
			<td></td>
		</tr>
		<tr>
			<td>Bullet Blender</td>
			<td>Next Advance</td>
			<td>BBX24</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge 5430</td>
			<td>Eppendorf</td>
			<td>22620509</td>
			<td></td>
		</tr>
		<tr>
			<td>Chloroform</td>
			<td>Fischer Scientific</td>
			<td>C298-500</td>
			<td></td>
		</tr>
		<tr>
			<td>CTAB solution</td>
			<td>Biosciences</td>
			<td>786-565</td>
			<td></td>
		</tr>
		<tr>
			<td>Dneasy Extraction Kit</td>
			<td>Qiagen</td>
			<td>69104</td>
			<td></td>
		</tr>
		<tr>
			<td>Filter Flask</td>
			<td>United</td>
			<td>FHFL1000</td>
			<td></td>
		</tr>
		<tr>
			<td>Filter Paper</td>
			<td>United Scientific Supplies</td>
			<td>FPR009</td>
			<td></td>
		</tr>
		<tr>
			<td>Gel Green 10000X</td>
			<td>Thomas Scientific</td>
			<td>B003B68 (1/EA)</td>
			<td></td>
		</tr>
		<tr>
			<td>Genie III</td>
			<td>OptiGene</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Hand pump</td>
			<td>Thomas Scientific</td>
			<td>1163B06</td>
			<td></td>
		</tr>
		<tr>
			<td>Iso-amyl Alcohol</td>
			<td>Fischer Scientific</td>
			<td>BP1150-500</td>
			<td></td>
		</tr>
		<tr>
			<td>LAVA LAMP master mix</td>
			<td>Lucigen</td>
			<td>30086-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnetic bead DNA extraction</td>
			<td>Genesig</td>
			<td>genesigEASY-EK</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnetic Separator</td>
			<td>Genesig</td>
			<td>genesigEASY-MR</td>
			<td></td>
		</tr>
		<tr>
			<td>polyvinylpyrrolidone</td>
			<td>Sigma Aldrich</td>
			<td>PVP40-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>Primers</td>
			<td>Sigma Aldrich</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Prism Mini Centrifuge</td>
			<td>Labnet</td>
			<td>C1801</td>
			<td></td>
		</tr>
		<tr>
			<td>T100 Thermal Cycler</td>
			<td>Bio-Rad</td>
			<td>1861096</td>
			<td></td>
		</tr>
		<tr>
			<td>UV Gel Doc</td>
			<td>Analytik Jena</td>
			<td>849-00502-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Warmstart Colorimetric Dye</td>
			<td>Lucigen</td>
			<td>E1800m</td>
			<td></td>
		</tr>
		<tr>
			<td>Wide Mini ReadySub-Cell GT Cell</td>
			<td>Bio-Rad</td>
			<td>1704489EDU</td>
			<td></td>
		</tr>
		<tr>
			<td>70% isopropanol</td>
			<td>Fischer Scientific</td>
			<td>A451-1</td>
			<td></td>
		</tr>
	</tbody>
</table>

detection of phytophthora capsici in irrigation water using loop-mediated isothermal amplification

Phytophthora capsici is a devastating oomycete pathogen that affects many important solanaceous and cucurbit crops causing significant economic losses in vegetable production annually. Phytophthora capsici is soil-borne and a persistent problem in vegetable fields due to its long-lived survival structures (oospores and chlamydospores) that resist weathering and degradation. The main method of dispersal is through the production of zoospores, which are single-celled, flagellated spores that can swim through thin films of water present on surfaces or in water-filled soil pores and can accumulate in puddles and ponds. Therefore, irrigation ponds can be a source of the pathogen and initial points of disease outbreaks. Detection of P. capsici in irrigation water is difficult using traditional culture-based methods because other microorganisms present in the environment, such as Pythium spp., usually overgrow P. capsici making it undetectable. To determine the presence of P. capsici spores in water sources (irrigation water, runoff, etc.), we developed a hand pump-based filter paper (8-10 &#181;m) method that captures the pathogen&#8217;s spores (zoospores) and is later used to amplify the pathogen&#8217;s DNA through a novel loop-mediated isothermal amplification (LAMP) assay designed for the specific amplification of P. capsici. This method can amplify and detect DNA from a concentration as low as 1.2 x 102 zoospores/mL, which is 40 times more sensitive than conventional PCR. No cross-amplification was obtained when testing closely related species. LAMP was also performed using a colorimetric LAMP master mix dye, displaying results that could be read with the naked eye for on-site rapid detection. This protocol could be adapted to other pathogens that reside, accumulate, or are dispersed via contaminated irrigation systems.

Optimization of LAMP method 
In this study, we detected the presence of Phytophthora capsici in irrigation water using a portable loop-mediated isothermal amplification (LAMP) assay. First, the proposed LAMP assay was optimized by testing different LAMP primer concentrations [F3, B3 (0.1&#8211;0.5 &#181;M each); LF, LB (0.5&#8211;1.0 &#181;M each) and FIP, BIP (0.8&#8211;2.4 &#181;M each)], durations (30&#8211;70 min), and temperatures (55&#8211;70 &#176;C). The final LAMP primer mix used i...

Watch this Scientific Journal Video about Detection of Phytophthora capsici in Irrigation Water using Loop-Mediated Isothermal Amplification at JoVE.com

Detection of Phytophthora capsici in Irrigation Water using Loop-Mediated Isothermal Amplification

We developed a method to detect Phytophthora capsici zoospores in water sources using a filter paper DNA extraction method coupled with a loop-mediated isothermal amplification (LAMP) assay that can be analyzed in the field or in the lab.

Detection of Phytophthora capsici in Irrigation Water using Loop-Mediated Isothermal Amplification

Phytophthora capsici is a devastating oomycete pathogen that affects many important solanaceous and cucurbit crops causing significant economic losses in ...

Phytopathogen detection is a crucial step in plant disease management. This protocol provides a rapid detection method for irrigation water contamination due to a common waterborne fighter pathogen. Using this technique, specific pathogen, such as Phytophthora capcici, can be processed and rapidly detected from our large volume of irrigation water while remaining on site.Demonstrating the procedure will be Owen Hudson, a Masters student from my laboratory, and Sumyya Waliullah, a PostDoctoral researcher from Dr.Pingxi G's laboratory to set up a pump and filter for on site Phytophthora capcici detection in irrigation water. Attach a filtering flask to a tube connected to a hand pump and fitted buchner funnel into the rubber stopper in the mouth of the filtering flask. Then fit an appropriately sized piece of filter paper with a 15 micron retention size into the funnel.To obtain water samples collect irrigation water from the targeted source. The water may have small amounts of debris, but not significant sediment or soil. Slowly pour between 50 to 1000 milliliters of test water over the filter paper inside the funnel while using the hand pump to create a suction to pull the water through the funnel.When all of the water has been filtered, use forceps to remove the filter paper from the funnel. And use sterile scissors to cut the paper into small pieces. Submerge eight to 12 pieces of paper in 400 microliters of extraction buffer in a 1.5 milliliter tube for a five minute incubation at room temperature.Vortex or otherwise agitate the paper for 10 seconds once every minute. At the end of the incubation, use forceps to remove the paper with as little buffer as possible. And repeat the license with the next set of filter paper pieces.For DNA extraction from the filter paper samples added 20 microliters of proteinase K and 10 microliters of 10 nanograms per microliter RNAs to the sample too and incubate the solution at room temperature for 15 minutes with vortexing or shaking every three minutes. At the end of the incubation, add 500 microliters of magnetic beads in binding buffer to the sample and mix well by shaking. After five minutes at room temperature, place the tube and the magnetic separator rack for two minutes before removing and discarding the supernatant.Remove the tube from the magnetic separator and vigorously re-suspend the beads in 500 microliters of wash buffer. After 30 seconds return the tube to the magnet and wait two minutes before discarding the supernatant. Repeat the wash with 500 microliters of wash buffer too and 500 microliters of 80%ethanol as just demonstrated.And air drive the magnetic bead pellet for 15 minutes at room temperature. At the end of the incubation re-suspend the beads in 50 microliters of elution buffer with pipetting for one minute before placing the tube back onto the magnet for two minutes to allow collection of the supernatant. After preparing the LAMP primer mix as indicated in the table, add at 2.5 microliters of primer mix 12.5 microliters of a lava LAMP mastermix one microliter of extracted DNA and nine microliters of double distilled water to a PCR tube and set up one positive and one negative control.incubate all of the samples in a 64 degrees Celsius heat blog for 45 minutes or the genie three amplification instrument at the end of the incubation, a load of five microliters of each amplified sample onto a 1%agarose gel and image the resulting bands on an ultraviolet imaging machine. If a calorimetric dye was used, view the color change to determine the results as positive or negative. If a portable amplification instrument was used, view the amplification graph on the screen to determine the results.The optical time for running the LAMP assay at 64 degrees is 45 minutes, as the lowest concentrations that were positive for detection are not amplified until 40 minutes, while higher concentrations are amplified at 20 minutes. Amplification can be confirmed on a 1%agarose gel labeled with a Nucleic acid stain. As illustrated conventional PCR is 40 times less sensitive than LAMP.Detecting 4.8 times 10 to the third zoospores per milliliter concentrations at the lowest. In this analysis, water samples were collected from seven ponds used for commercial vegetable production in Tift County, Georgia. Three of which demonstrated positive LAMP results.When the samples were tested by conventional PCR however, zoospores were detected in only one of the three positive samples. In this table, the differences between detection methods using such variables as sensitivity, time, required preparation, materials and cost are summarized. LAMP is the least expensive method among the tested methods, and is also the fastest, requiring only 30 to 60 minutes for amplification compared to conventional PCR amplification.Using this protocol DNA extracted from closely related UMI seed pathogens results in no detection for any of the samples, confirming the specificity of the primers. Make sure not to pour the sample water too fast and be careful when adding extracted DNA to the LAMP tubes to limit contamination. Once other waterborne pathogens have had their specific primer sets developed, the filtration and lamp acid methods can be adapted for other pathogens.

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JoVE Journal

Environment

6.3K Views.  University of Georgia. Il rilevamento dei fitopatogeni è un passo cruciale nella gestione delle malattie delle piante. Questo protocollo fornisce un metodo di rilevamento rapido per la contaminazione dell'acqua di irrigazione a causa di un comune agente patogeno da combattimento aviotrasportato dall'acqua. Utilizzando questa tecnica, agenti patogeni specifici, come Phytophthora capcici, possono essere lavorati e rapidamente rilevati dal nostro grande volume di acqua di irrigazione pur rimanendo in loco.A di...